Substituted heterocycle fused gamma-carbolines are known to be agonists or antagonists of 5-HT2 receptors, particularly 5-HT2A and 5-HT2C receptors, in treating central nervous system disorders. These compounds have been disclosed in U.S. Pat. Nos. 6,548,493; 7,238,690; 6,552,017; 6,713,471; 7,183,282; U.S. RE39680, and U.S. RE39679, as novel compounds useful for the treatment of disorders associated with 5-HT2A receptor modulation such as obesity, anxiety, depression, psychosis, schizophrenia, sleep disorders, sexual disorders migraine, conditions associated with cephalic pain, social phobias, gastrointestinal disorders such as dysfunction of the gastrointestinal tract motility, and obesity.
PCT/US08/03340 (WO 2008/112280) and U.S. application Ser. No. 10/786,935 disclose methods of making substituted heterocycle fused gamma-carbolines and uses of these gamma-carbolines as serotonin agonists and antagonists useful for the control and prevention of central nervous system disorders such as addictive behavior and sleep disorders.
WO/2009/145900 discloses use of particular substituted heterocycle fused gamma-carbolines for the treatment of a combination of psychosis and depressive disorders as well as sleep, depressive and/or mood disorders in patients with psychosis or Parkinson's disease. In addition to disorders associated with psychosis and/or depression, this patent application discloses and claims use of these compounds at a low dose to selectively antagonize 5-HT2A receptors without affecting or minimally affecting dopamine D2 receptors, thereby useful for the treatment of sleep disorders without the side effects of the dopamine D2 pathways or side effects of other pathways (e.g., GABAA receptors) associated with conventional sedative-hypnotic agents (e.g., benzodiazepines) including but not limited to the development of drug dependency, muscle hypotonia, weakness, headache, blurred vision, vertigo, nausea, vomiting, epigastric distress, diarrhea, joint pains, and chest pains.
Furthermore, it has been discovered that these substituted heterocycle fused gamma-carboline compounds are effective in treating not just acute symptoms, but also residual symptoms of psychosis. Therefore, methods of using these substituted heterocycle fused gamma-carboline compounds, either alone or as an adjunctive therapy for the treatment of residual symptoms of psychosis, particularly schizophrenia, were disclosed. See for example, application PCT/US2014/68443.
WO 2009/114181 discloses methods of preparing toluenesulfonic acid addition salt crystals of particular substituted heterocycle fused gamma-carbolines, e.g., toluenesulfonic acid addition salt of 4-((6bR,10aS)-3-methyl-2,3,6b,9,10,10a-hexahydro-1H-pyrido[3′,4′:4,5]pyrrolo[1,2,3-de]quinoxalin-8(7H)-yl)-1-(4-fluorophenyl)-1-butanone.
WO 2011/133224 discloses prodrugs/metabolites of substituted heterocycle fused gamma-carboline for improved formulation, e.g., extended/controlled release formulation. This application discloses that heterocycle fused gamma-carboline N-substituted with a 4-fluorophenyl(4-hydroxy)butyl moiety are shown to have high selectivity for the serotonin transporter (SERT) relative to the heterocycle fused gamma-carboline containing 4-fluorophenylbutanone. The hydroxy group on these compounds, however, is inter-converted to and from the ketone within the plasma and the brain, allowing it to serve as a reservoir for the 4-fluorophenylbutanone drug. While substituted heterocycle fused gamma-carbolines and their uses are known, our inventors have surprisingly found that particular substituted heterocycle fused gamma-carbolines, while less active in in-vitro tests, are inter-converted between these less active compounds and the highly active ketone drug within the plasma and the brain. Our inventors have further provided prodrugs of particular substituted heterocycle fused gamma-carbolines that have altered pharmacokinetic profile, e.g., altered mechanisms and/or rate of absorption and distribution, and therefore may be useful for an improved formulation and/or for controlling the duration of the effect of the drug in the body (e.g., for sustained- or controlled release).
WO 2013/155505 discloses compounds which block the in vivo inter-conversion between the hydroxy and the ketone, by incorporating an alkyl substituent on the carbon bearing the hydroxyl group, thus yielding compounds which antagonize 5-HT2A receptors and also inhibit serotonin re-uptake transporter.
The major routes of metabolism of the compounds previously disclosed are N-demethylation catalyzed by CYP 3A4, and ketone reduction catalyzed by ketone reductase. N-dealkylation by cytochrome oxidase enzymes is known to occur via an initial oxidation of one or more of the carbon atoms alpha to the nitrogen atom. The family of enzymes that catalyze ketone reduction is large and varied, and the mechanism has not been absolutely elucidated. It is of interest that, mechanistically, ketone reduction may operate either by way of the enol tautomer of the ketone or the keto tautomer.